Fix to not give hints by putting answers found so far in their alphabetical position.

Fix to not give hints by putting answers found so far in their alphabetical position.

Instead all found answers now appear alphabetically before the blanks
corresponding to all unfound answers.

Part of implementing this was adding new of_length interfaces to dict
in place (or in addition) to the previous by_length interfaces. The
new interfaces are much more useful, (allowing length-limited queries
without any implicit looping).